In order to recover oils from certain geologic formations, injection of steam increases mobility of the oil within the formation via, for example, a process known as steam assisted gravity drainage (SAGD). Energy needed for steam generation represents a substantial cost for the SAGD. Ability to provide cost efficient recovery of the oils with the SAGD diminishes as zones for oil bearing formations decrease in thickness.
In situ combustion offers another approach for recovering the oil. With in situ combustion, an oxidant injected through an injection well into the formation reacts with some of the oil to propagate a combustion front through the formation. This process heats the oil ahead of the combustion front while the injection gas and combustion gas products drive the oil that is heated toward an adjacent production well.
Vertical stratification further presents problems with respect to recovery processes such as the SAGD and the in situ combustion since separate formations may be separated from one another by natural barriers. One or more of the separate formations may be too thin for economic recovery utilizing the SAGD. Further, the separate formations can present various control problems with the in situ combustion. For example, the injection and/or production wells utilized for the in situ combustion processes may lead to premature unregulated breakthrough across the separate formations, such as when producing, and may burn up prior to full recovery of the oil without proper control for each of the separate formations.
Therefore, a need exists for improved methods and systems for oil recovery with in situ combustion.